Many systems, for example, radar and radio systems, use an internal clock signal for proper operation and synchronization. In these systems, the internal clock signal is generated by a clock signal source, for example, a temperature compensated crystal oscillator (TCXO) or a voltage controlled crystal oscillator (VCXO).
The clock signal generated by the clock signal source, however, drifts over time and the frequency changes value. If the amount of frequency drift is too much, the system may not operate properly. In many instances, the frequency of the clock signal source can only be adjusted when the whole system is taken off line for maintenance.
What is needed is an approach to controlling a clock signal source operating in a system.